At its inception radio telephony was designed, and used for, voice communications. As the consumer electronics industry continued to mature, and the capabilities of processors increased, more devices became available for use that allowed the wireless transfer of data between devices. Also more applications became available that operated based on such transferred data. Of particular note are the Internet and local area networks (LANs). These two innovations allowed multiple users and multiple devices to communicate and exchange data between different devices and device types. With the advent of these devices and capabilities, users (both business and residential) found an increasing need to transmit data, as well as voice, from mobile locations.
The infrastructure and networks which support this voice and data transfer have likewise evolved. Limited data applications, such as text messaging, were introduced into the so-called “2G” systems, such as the Global System for Mobile (GSM) communications. Packet data over radio communication systems were implemented in GSM with the addition of the General Packet Radio Services (GPRS), sometimes referred to as a “2G+” system. 3G systems introduced by Universal Terrestrial Radio Access (UTRA) standards made applications like surfing the web more easily accessible to millions of users (and with more tolerable delay), and now 4G systems such as those operating in accordance with the Long Term Evolution (LTE) standard are being rolled out and into service. Thus, numerous radio access technologies (RATs), such as e.g. Wideband Code Division Multiple Access (WCDMA), OFDMA, TDMA, TD-SCDMA, and others, can be found in use today in wireless systems such as e.g. GSM/GPRS/EDGE, UMTS, UMTS-LTE, WLAN, WiFi, etc.
This evolution of network designs has resulted in various network operators deploying their networks in various frequency bands with different RATs in various geographical areas. As a result of this, a radio communication device or user equipment (UE) which supports several frequency bands and/or several different RATs will need to be able to, among other things, deal with issues which arise from implementing such devices having radios with, e.g., overlapping frequency bandwidths. The resolution of such issues is frequently referred to as “co-existence management”, i.e., the provision of a capability to allow potentially interfering radios to operate in close proximity to one another.
In addition to co-existence issues which arise in the context of multiple radios, similar issues arise in radio devices which are architected as embedded systems. For example, many of today's portable devices are architected as embedded systems having specialized processors (DSPs) which handle specific functions, such as interfacing with a display, camera or multimedia card and operating as a memory controller. Each of these devices may have its own clock or clock signal which can generate harmonics at frequencies which are the same as those used by the radio in the portable device. Such harmonics interfere with the operation of the radio by “leaking” energy into the receiver circuitry at a conflicting frequency thereby reducing receiver sensitivity.
Such problems are particularly significant in radio devices which operate in accordance with, for example, the 2G/2G+ standard (i.e., GSM/GPRS/EGPRS). This is because for 2G/2G+ devices there is a relatively small bandwidth for a given radio channel (i.e., a 200 kHz channel), making such devices more sensitive to this type of interference. By way of comparison a 3G radio channel is typically 4 MHz in bandwidth and an LTE radio channel is typically 1.5 MHz to 20 MHz in bandwidth.
Various solutions have been proposed, which are sometimes generally referred to as immunity management techniques, i.e., techniques which immunize circuitry from sensitivity clock harmonics. In general, one solution to this problem is to slightly change the clock frequency of the processor (sometimes referred to as the “aggressor” in co-existence or immunity terms) which is generating conflicting harmonics with the radio (sometimes referred to as the “victim” in co-existence or immunity terms). However this frequency changing solution is problematic for radio devices which operate using frequency hopping techniques, e.g., systems wherein the channel frequency allocated to the radio device changes periodically during the connection. For example, in 2G/2G+ systems, the frequency allocated to a particular channel changes (hops) every 5 ms. In such a frequency hopping system then, if a change is made to an aggressor's clock frequency to address harmonics associated with a radio's reception of signals at a first hopping frequency, that change may no longer be valid 5 ms later when the radio channel's frequency changes to a second hopping frequency. Moreover, for various reasons, it is impractical to change the clock frequency of an aggressor's clock signal every 5 ms, e.g., due to potential instability and/or latency issues.
Accordingly, it would be desirable to provide methods, devices and systems which address these, and other, challenges.